Re: Linux DRTM on UEFI platforms

[Ard Biesheuvel]

On Wed, 30 Mar 2022 at 09:11, Matthew Garrett <mjg59@srcf.ucam.org> wrote:
>
> On Wed, Mar 30, 2022 at 09:02:18AM +0200, Ard Biesheuvel wrote:
>
> > Wouldn't it be better for the secure launch kernel to boot the EFI
> > entrypoint directly? As it happens, I just completed a PoC last week
> > for a minimal implementation of EFI (in Rust) that only carries the
> > pieces that the EFI stub needs to boot Linux. It is currently just a
> > proof of concept that only works on QEMU/arm64, but it should not be
> > too hard to adapt it for x86 and for booting a kernel that has already
> > been loaded to memory.
>
> The EFI stub carries out a bunch of actions that have meaningful
> security impact, and that's material that should be measured. Having the
> secure launch kernel execute the stub without awareness of what it does
> means it would need to measure the code without measuring the state,
> while the goal of DRTM solutions is to measure state rather than the
> code.

But how is that any different from the early kernel code?